Billboard Cover: A Candid Conversation With Demi Lovato & Nick Jonas on Surviving Disney, Their Huge New Tour and Pop Stardom on Their Own Terms You've known Nick all of his life and Demi for most of yours.

Are you surprised that these two kids from are doing this huge tour together now?

It's surprising just in the world we live in -- it's tough to stay friends with people who are in the industry over this much time. They've seen each other go through so much, personally and in their careers.

It's cool to see this bond now that they're adults. You'd think they're siblings, sometimes more than Nick and I. Demi's a great listener, and she keeps Nick smiling -- she'll always make a serious situation laughable. It's difficult to take a backseat and say, "Let's work together and figure out something great." I commend them both for that.

I think it's nice for an audience as well -- they get to watch Nick and Demi grow up, not only together, but also musically. So, they've found great support with one another and they lean on each other creatively. Demi Lovato & Nick Jonas: A Timeline of Their Friendship Demi talks about writing "Gonna Get Caught" when you two were dating.

Was it weird to know your brother was helping her write songs about you?

I was oblivious to that until I was asked to step out of a songwriting session or two, then it started to be a little clearer what this was about. I'll be honest, I was a bit envious when I saw him catapult into this personal success. "Pop's Boy-Girl Pals -- From Taylor Swift & Ed Sheeran to Rihanna & Drake You've seen Demi go through it. She's the best version of herself I've ever known.

[] We've seen each other go through tough times, good times, in and out of relationships. It feels like we were children, although I guess we were. I was hungry for it, but it's something you can't rush and Nick's always creative -- his favorite hang time is in the studio. She's healthy and that's obviously something a lot of the world knows now, but she's gotten over [the really hard part]. One thing about my brother that drives me crazy is he's very competitive.